FRANKFURT, Nov 3 (Reuters) - Police and tax investigators raided the headquarters of Germany's football association (DFB) on Tuesday and searched the homes of officials to investigate suspected tax evasion linked to the awarding of the 2006 World Cup, prosecutors said.

The raids focused on 6.7 million euros ($7.4 million) the DFB transferred to world soccer's governing body FIFA in 2005 - adding another layer to U.S. and Swiss investigations into allegations of corruption in the awarding of the 2018 and 2022 World Cups to Russia and Qatar.

The Frankfurt state prosecutor last month launched a monitoring process - a step before a formal investigation - into the payment.

A spokeswoman said on Tuesday any other suspicion of wrongdoing, such as bribery or corruption, would not be followed up due to the statute of limitations.

Now the investigation will just focus on tax implications, which must be examined within 10 years.

Prosecutors said Wolfgang Niersbach, the president of the DFB, his predecessor Theo Zwanziger and the association's former general secretary, Horst Schmidt, who all held senior positions on the 2006 organising committee, are suspected of tax evasion over the payment for failing to register the payment properly in tax returns.

Lawyers for Niersbach and Schmidt declined to comment. Zwanziger welcomed the raids and said he wanted the truth to come out.

"The Frankfurt state prosecutor has launched an investigation on suspicion of tax evasion in an especially serious way in relation with the awarding of the 2006 World Cup and the money transfer of 6.7 million euros from the World Cup organising committee to FIFA," the prosecutor said in a statement.

The DFB and the prosecutor said the association itself was not being investigated.

DOCUMENTS SEIZED

The investigation stems from a Der Spiegel magazine report in October that suggested a slush fund had been used to buy votes for the German bid in 2000.

It alleged that deceased Adidas CEO Robert Louis-Dreyfus loaned the money to the German bid committee to buy votes at the FIFA election. Germany won by a single vote from South Africa.

It said the DFB returned the same sum to Louis-Dreyfus via FIFA in 2005. Adidas, a major sponsor of the DFB, declined to comment on the raids.

Niersbach and Franz Beckenbauer, head of the 2006 organising committee, have vehemently denied those accusations, along with the DFB itself. Niersbach told reporters last month there were no slush funds and there was no vote purchase.

Zwanziger, who led the DFB from 2006-2012, said on Tuesday he was only interested in the truth.

"(I want) the truth to finally come out and not by an investigation carried out by the DFB. I am happy it came this way," Zwanziger told reporters.

"I have no worries. I am totally relaxed. What else might come out of it we will see. But it is better this way than through some kind of investigation committees by people who are involved."

The payment is being investigated in-house by both the DFB and FIFA. The DFB said in a statement on Tuesday it was cooperating with the prosecutor's tax investigation.

"The DFB offered the investigators its full cooperation in the clarification of the accusations," it said.

"The prosecutor's office said the raids were part of an investigation into suspicion of a tax offence. The DFB itself is not among those accused."

The prosecutor said the 2005 payment was registered in returns as an operational expense, meaning the trio avoided a number of different taxes that should have been paid on it.

Prosecutor's office spokeswoman Nadja Niesen said charges could be filed pending the findings of the raids, which involved more than 50 officers and netted written and electronic documents.

She said tax evasion on a serious level carried a prison sentence of anywhere between six months and 10 years.

Niersbach was invited to a hearing of the parliamentary committee on sport on Wednesday that he has declined to attend.

Reacting to the raids, committee member Oezcan Mutlu said: "This is not surprising because at the end of the day the DFB did not make efforts for transparency and clarification." ($1 = 0.9098 euros) (Reporting by Andreas Kroener in Frankfurt and Madeline Chambers; Writing by Karolos Grohmann; Editing by Alison Williams)